铁在不同温度和湿度环境中形成不同铁的化合物,如铁的氧化物、氢氧化物、硫化物和碳酸盐等。这些不同种类含铁矿物可以通过磁学方法测量,根据它们含量与比例特征来分析过去地球环境变化。黄土是一种风积形成特殊成因的沉积岩,经过百余年不断争论,才有了“风成”的定论。本文总结概括世界各地的黄土古土壤形成环境与铁矿物特征,得到如下认识:红色古土壤只形成于干旱氧化环境中,但不是所有干旱条件都能够形成红色土;红色土壤中的磁赤铁矿和赤铁矿在湿润氧化和还原环境中不稳定,会渐渐转变成为氢氧化物(褐铁矿),甚至硫化物(黄铁矿/磁黄铁矿),导致红色褪去、黄色增加和磁化率降低。现代的河流、湖泊和海洋均为还原环境,沉积物也呈黄、灰、白、绿、黑等还原系列颜色与之对应。将今论古可以推理,过去红色地层极不可能形成于“水成”环境,只能形成于地表透水性良好的干燥氧化环境中。沉积岩除了“水成”和“风成”两个大类环境之外,至少还有一种过渡交互类型需要得到特别认识,如干旱区山间盆地洪积类型(戈壁滩洪积与河流河漫滩等环境)。这类沉积物毫无疑问是洪水搬运形成,因此留下层理等特征;但是洪水消失后,沉积物实际上长期处于地表干燥氧化成土环境,因此兼有水成和成土两种特征。丹霞红层具有水成层理,并同时具有原生红颜色的就是在这样环境中形成的。张掖彩色丘陵,并非湖相水成地层,而主要是风积古土壤地层序列,在长期持续炎热半干旱环境条件下甚至还发育了特殊的厚层石膏土。黄土与环境的深入研究必将对地质学和地理学产生深远的影响,比如黄土研究已经带来地学一些基本概念变化,如:古土壤层并不一定意味着沉积间断;层状沉积岩地层并不一定是“水成”等等。 Iron forms compounds of different iron in different temperature and humidity environments, such as iron oxides, hydroxides, sulfides and carbonates. These different types of iron-bearing minerals can be magnetically measured and analyzed for past earth environment changes based on their content and proportionality characteristics. Loess is a sedimentary rock with special genesis of aeolian accumulation. After more than 100 years of continuous debate, there is a conclusion that “loess is a wind”. This paper summarizes the characteristics of the formation of environment and iron minerals in the loess paleosol around the world and gets the following recognition: the ancient red soil was only formed in the arid and oxidative environment, but not the red soil could be formed under all drought conditions; the magnetic hematite Molybdenum and hematite are not stable in wet oxidation and reduction environments, and will gradually transform into hydroxides (limonite) and even sulfides (pyrite / pyrrhotite) resulting in red fading, yellowing and magnetization Lower rates. Modern rivers, lakes and oceans are reducing environment, sediment also yellow, gray, white, green, black and other reduction series color corresponding. This theory can be reasoned that in the past, the red formation was extremely unlikely to be formed in an “aquatic” environment and could only be formed in a dry, oxidized environment with good water permeability on the surface. Sedimentary rock In addition to the “water into” and “wind into” two broad categories of environment, at least one type of transitional interaction needs to be particularly recognized, such as alluvial types of arid basin mountain basin (Gobi Desert and River floodplain and other environment). This type of sediment is undoubtedly formed by the flood handling, thus leaving the stratification and other characteristics. However, after the flood disappeared, the sediments were actually exposed to the earth’s surface for an extended period of time and were thus oxidized into soils. Danxia red layer with water layering, and at the same time with the original red color is formed in such an environment. The colored hills in Zhangye are not strata of the lake facies, but mainly are sequences of volcanic and paleosol strata that even developed special thick gypsum plaster under long-term and continuous hot and semi-arid environment. In-depth study of the loess and the environment will certainly have a profound impact on geology and geography. For example, loess research has led to some basic concepts such as: the ancient soil layer does not necessarily mean that sedimentary discontinuities; layered sedimentary rock formation is not Must be “water into” and so on.